Light emitting diode, method of manufacturing the same and display device including the same

ABSTRACT

A light emitting element (e.g., light emitting diode) includes a first electrode, a hole transport region on the first electrode, an emission layer on the hole transport region and containing a quantum dot complex, an electron transport region on the emission layer, and a second electrode on the electron transport region, wherein the quantum dot complex contains two or more quantum dots each including a core and a shell surrounding the core, the shell of one quantum dot is combined with a shell of at least one neighboring quantum dot, and the light emitting element (e.g., light emitting diode) may thus have improved luminous efficiency and service life.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2021-0001988, filed on Jan. 7, 2021, in the KoreanIntellectual Property Office, the entire content of which is herebyincorporated by reference.

BACKGROUND 1. Field

The present disclosure herein relates to a light emitting element (e.g.,light emitting diode), a method of manufacturing the same, and a displaydevice including the same.

2. Description of Related Art

Various kinds (e.g., types) of display devices utilized for multimediadevices such as a television set, a mobile phone, a tablet computer, anavigation system, and/or a game console are being developed. In suchdisplay devices, a so-called self-luminescent display element isutilized, which accomplishes display by causing an organiccompound-containing light emitting material to emit light.

In addition, the development of light emitting elements (e.g., lightemitting diodes) utilizing quantum dots as a light emitting material isunderway in an effort to enhance the color reproducibility of displaydevices, and there is a demand (e.g., need) for increasing the luminousefficiency and lifespan of the light emitting elements (e.g., lightemitting diodes) utilizing quantum dots.

SUMMARY

One or more aspects according to embodiments of the present disclosureare directed toward a light emitting element (e.g., light emittingdiode) and a display device having improved luminous efficiency andlifespan, including an emission layer containing a plurality of quantumdots in close distance to each other.

One or more aspects according to embodiments of the present disclosureare directed toward a method of manufacturing a light emitting element(e.g., light emitting diode) including forming a bond between shells(e.g., of neighboring quantum dots) through providing energy (e.g., theprovision of specific energy) to improve film density.

According to an embodiment of the present disclosure, a light emittingelement (e.g., light emitting diode) includes a first electrode, a holetransport region on the first electrode, an emission layer on the holetransport region and including a quantum dot complex, an electrontransport region on the emission layer, and a second electrode on theelectron transport region, wherein the quantum dot complex includes twoor more quantum dots each including a core and a shell around (e.g.,surrounding) the core, and of the two or more quantum dots, the shell ofone quantum dot is combined with a shell of at least one neighboringquantum dot.

In an embodiment, the emission layer may further include low meltingpoint particles, wherein the low melting point particles include a metaland/or an alloy having a melting point of 1300° C. or less.

In an embodiment, the low melting point particles may include at leastone from among Al, Mg, Zn, Sn, Mn, Cu, and an alloy thereof.

In an embodiment, a weight ratio of the low melting point particles tothe quantum dots may be about 1:200 to about 1:20.

In an embodiment, each of the low melting point particles may have asize of 1 μm or less.

In an embodiment, the shell may include at least one from among CdS,CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnSeS, ZnTeS, GaAs, GaP, GaSb, HgS, HgSe,HgTe, InAs, InP, InGaP, InSb, AlAs, AIP, and AlSb.

In an embodiment, the hole transport region may include organicmaterials, and the electron transport region may include inorganicmaterials.

In an embodiment of the present disclosure, a display device includes aplurality of light emitting elements (e.g., light emitting diodes), anda light conversion layer on the plurality of light emitting elements(e.g., light emitting diodes) and including at least one light controlunit including a quantum dot complex, wherein the quantum dot complexincludes two or more quantum dots each including a core and a shellaround the core, and of the two or more quantum dots, the shell of onequantum dot is combined with a shell of at least one neighboring quantumdot.

In an embodiment, the light emitting elements (e.g., light emittingdiodes) may emit a first color light, and the light control unit mayinclude a transmission unit to transmit the first color light, a firstlight control unit to convert the first color light into a second colorlight, and a second light control unit to convert the first color lightinto a third color light.

In an embodiment, the light control unit may further include low meltingpoint particles, wherein the low melting point particles may include ametal and/or an alloy having a melting point of 800° C. or less.

In an embodiment, the display device may further include a color filterlayer on the light emitting elements (e.g., light emitting diodes),wherein the color filter layer may include a first filter to transmitthe first color light, a second filter to transmit the second colorlight, and a third filter to transmit the third color light.

In an embodiment of the present disclosure, a method of manufacturing alight emitting element (e.g., light emitting diode) includes providing afirst electrode, forming a hole transport region on the first electrode,forming an emission layer on the hole transport region, forming anelectron transport region on the emission layer, and forming a secondelectrode on the electron transport region, wherein the forming of theemission layer includes preparing a quantum dot composition including aplurality of quantum dots having a core and a shell around the core,providing the quantum dot composition to form a preliminary emissionlayer, and providing energy to the preliminary emission layer such thata temperature of the preliminary emission layer reaches about 30% toabout 80% of a melting point of the shell.

In an embodiment, the quantum dot composition may further include lowmelting point particles.

In an embodiment, the preparing of the quantum dot composition may beperformed by dispersing the plurality of quantum dots in an organicsolvent.

In an embodiment, the method may further include binding a ligand to theplurality of quantum dots before the dispersing of the plurality ofquantum dots in an organic solvent.

In an embodiment, in the providing of energy to the preliminary emissionlayer, the ligand may be dissociated from the plurality of quantum dots.

In an embodiment, the forming of the emission layer and the forming ofthe electron transport region on the emission layer may be performedthrough inkjet printing.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present disclosure, and are incorporated in andconstitute a part of this specification. The drawings illustrateembodiments of the present disclosure and, together with thedescription, serve to explain principles of the present disclosure. Inthe drawings:

FIG. 1 is a plan view of a display device according to an embodiment ofthe present disclosure;

FIG. 2 is a cross-sectional view of a display device according to anembodiment of the present disclosure;

FIG. 3 is a cross-sectional view schematically illustrating a lightemitting element (e.g., light emitting diode) according to an embodimentof the present disclosure;

FIG. 4A is a cross-sectional view illustrating an emission layeraccording to an embodiment;

FIG. 4B is a cross-sectional view illustrating an emission layeraccording to an embodiment;

FIG. 5 is a flowchart illustrating a method of manufacturing a lightemitting element (e.g., light emitting diode) according to anembodiment;

FIG. 6 is a cross-sectional view schematically illustrating forming anemission layer in a method of manufacturing a light emitting element(e.g., light emitting diode) according to an embodiment;

FIG. 7 is a cross-sectional view illustrating a portion of a quantum dotcomposition provided in FIG. 6 in more detail;

FIG. 8 is a schematic view illustrating a part of a method ofmanufacturing a light emitting element (e.g., light emitting diode)according to an embodiment;

FIG. 9A is a graph showing results of analyzing luminous efficiencyaccording to the thickness of shells;

FIG. 9B is a graph showing results of analyzing lifespan according tothe thickness of shells; and

FIG. 10 is a cross-sectional view of a display device according to anembodiment.

DETAILED DESCRIPTION

The present disclosure may be modified in many alternate forms, and thusspecific embodiments will be illustrated in the drawings and describedin more detail. It should be understood, however, that it is notintended to limit the present disclosure to the particular formsdisclosed, but rather, is intended to cover all modifications,equivalents, and alternatives falling within the spirit and scope of thepresent disclosure.

In the present description, when an element (or a region, a layer, aportion, etc.) is referred to as being “on,” “connected to,” or “coupledto” another element, it refers to that the element may be directlydisposed on/connected to/coupled to the other element, or that a thirdelement may be disposed therebetween.

In the present description, the term “directly disposed” or “directlyon” may indicate that there is no layer, film, region, plate and/or thelike added between a portion of a layer, a film, a region, a plateand/or the like and other portions. For example, “directly disposed” or“directly on” may indicate no additional members such as an adhesivemember exist between two layers or two members.

Like reference numerals refer to like elements. Also, in the drawings,the thickness, the ratio, and the dimensions of elements may beexaggerated for an effective description of technical contents.

The term “and/or,” includes any and all combinations of one or more ofthe associated listed items.

It will be understood that, although the terms “first”, “second”, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Theterms of a singular form may include plural forms unless the contextclearly indicates otherwise.

In addition, terms such as “below,” “lower,” “above,” “upper,” and/orthe like are used to describe the relationship between the componentsshown in the drawings. The terms are used as a relative concept and aredescribed with reference to the direction indicated in the drawings.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the present disclosure pertains.It is also to be understood that terms defined in commonly useddictionaries should be interpreted as having meanings consistent withthe meanings in the context of the related art, and should not beinterpreted in an ideal or overly formal sense unless they are expresslydefined herein.

It should be understood that the terms “comprise”, or “have” areintended to specify the presence of stated features, integers, steps,operations, elements, components, or combinations thereof in thedisclosure, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components, orcombinations thereof.

Hereinafter, a quantum dot composition, a light emitting element (e.g.,light emitting diode), and a display device including the same accordingto an embodiment of the present disclosure will be described withreference to the accompanying drawings.

FIG. 1 is a plan view illustrating an embodiment of a display device DD.FIG. 2 is a cross-sectional view of a display device DD according to anembodiment. In particular, FIG. 2 is a cross-sectional view showing aportion corresponding to the line I-I′ of FIG. 1.

The display device DD may include a display panel DP and an opticallayer PP disposed on the display panel DP. The display panel DP mayinclude light emitting elements (e.g., light emitting diodes) ED-1,ED-2, and ED-3. The display device DD may include a plurality of lightemitting elements (e.g., light emitting diodes) ED-1, ED-2, and ED-3.The optical layer PP may be disposed on the display panel DP to controlreflected light in the display panel DP due to external light. Theoptical layer PP may include, for example, a polarizing layer and/or acolor filter layer. In one or more embodiments, unlike the one in thedrawings, the optical layer PP may be omitted in the display device DDof an embodiment.

In the display device DD of an embodiment, the display panel DP may be alight emitting display panel. For example, the display panel DP may be aquantum dot light emitting display panel containing quantum dot lightemitting elements (e.g., light emitting diodes). However, the presentdisclosure is not limited thereto.

The display panel DP may include a base substrate BS, a circuit layerDP-CL provided on the base substrate BS, and a display element layerDP-EL. The display element layer DP-EL may include a pixel defining filmPDL, a plurality of light emitting elements (e.g., light emittingdiodes) ED-1, ED-2, and ED-3 disposed between the pixel defining filmPDL, and an encapsulation layer TFE disposed on the plurality of lightemitting elements (e.g., light emitting diodes) ED-1, ED-2, and ED-3.

The base substrate BS may be a member providing a base surface on whichthe display element layer DP-EL is disposed. The base substrate BS maybe a glass substrate, a metal substrate, a plastic substrate, etc.However, the present disclosure is not limited thereto, and the basesubstrate BS may be an inorganic layer, an organic layer, or a compositematerial (e.g., a complex material, including an inorganic material andan organic material) layer. The base substrate BS may be a flexiblesubstrate that may be readily bent or folded.

In an embodiment, the circuit layer DP-CL may be disposed on the basesubstrate BS, and the circuit layer DP-CL may include a plurality oftransistors. The transistors each may include a control electrode, aninput electrode, and an output electrode. For example, the circuit layerDP-CL may include a switching transistor and a driving transistor fordriving a plurality of light emitting elements (e.g., light emittingdiodes) ED-1, ED-2 and ED-3 of the display element layer DP-EL.

The light emitting elements (e.g., light emitting diodes) ED-1, ED-2,and ED-3 each may have a structure of a light emitting element (e.g.,light emitting diode) ED according to an embodiment shown in FIGS. 3 to6, which will be described in more detail later. The light emittingelements (e.g., light emitting diodes) ED-1, ED-2, and ED-3 each mayinclude a first electrode EL1, a hole transport region HTR, acorresponding one of emission layers EML-R, EML-G, and EML-B, anelectron transport region ETR, and a second electrode EL2.

FIG. 2 illustrates an embodiment in which the emission layers EML-R,EML-G, and EML-B of the light emitting elements (e.g., light emittingdiodes) ED-1, ED-2, and ED-3 are disposed in openings OH defined in thepixel defining film PDL, and the hole transport region HTR, the electrontransport region ETR, and the second electrode EL2 are provided as acommon layer throughout the light emitting elements (e.g., lightemitting diodes) ED-1, ED-2, and ED-3. However, the present disclosureis not limited thereto, and unlike the one shown in FIG. 2, in anembodiment, the hole transport region HTR and the electron transportregion ETR may be provided to be patterned inside the openings OHdefined in the pixel defining film PDL. For example, in an embodiment,the hole transport region HTR, the emission layers EML-R, EML-G, andEML-B, and the electron transport region ETR, etc. of the light emittingelements (e.g., light emitting diodes) ED-1, ED-2, and ED-3 may beprovided to be patterned through an inkjet printing method.

The pixel defining film PDL may be formed of a polymer resin. Forexample, the pixel defining film PDL may be formed from materialsincluding a polyacrylate-based resin and/or a polyimide-based resin. Inaddition, the pixel defining film PDL may be formed by further includingan inorganic material in addition to the polymer resin. In someembodiments, the pixel defining film PDL may be formed to furtherinclude a light absorbing material, or may be formed to further includea black pigment and/or a black dye. The pixel defining film PDL formedto further include a black pigment and/or a black dye may implement(e.g., produce) a black pixel defining film. When forming the pixeldefining film PDL, carbon black may be utilized as a black pigmentand/or a black dye, but the present disclosure is not limited thereto.

In some embodiments, the pixel defining film PDL may be formed of aninorganic material. For example, the pixel defining film PDL may beformed from materials including silicon nitride (SiNx), silicon oxide(SiOx), silicon oxide (SiOxNy), etc. The pixel defining film PDL maydefine light emitting areas PXA-B, PXA-G, and PXA-R. The light emittingareas PXA-B, PXA-G, and PXA-R, and a non-light emitting area NPXA may beseparated by the pixel defining film PDL.

An encapsulation layer TFE may cover the light emitting elements (e.g.,light emitting diodes) ED-1, ED-2 and ED-3. The encapsulation layer TFEmay seal the display element layer DP-EL. The encapsulation layer TFEmay be a thin film encapsulation layer. The encapsulation layer TFE maybe a single layer or a laminated layer of a plurality of layers. Theencapsulation layer TFE includes at least one insulating layer. Theencapsulation layer TFE according to an embodiment may include at leastone inorganic film (hereinafter, an encapsulation inorganic film). Insome embodiments, the encapsulation layer TFE according to an embodimentmay include at least one organic film (hereinafter, an encapsulationorganic film) and at least one encapsulation inorganic film.

The encapsulation inorganic film protects the display element layerDP-EL from moisture/oxygen, and the encapsulation organic film protectsthe display element layer DP-EL from foreign substances such as dustparticles. The encapsulation inorganic film may include silicon nitride,silicon oxy nitride, silicon oxide, titanium oxide, aluminum oxide,etc., but the present disclosure is not particularly limited thereto.The encapsulation organic layer may include an acrylic-based compound,an epoxy-based compound, etc. The encapsulation organic layer mayinclude a photopolymerizable organic material, and is not particularlylimited.

The encapsulation layer TFE may be disposed on the second electrode EL2,and may be disposed to fill the opening OH. In some embodiments, acapping layer CPL may be further disposed between the second electrodeEL2 and the encapsulation layer TFE. The capping layer CPL may include amultilayer or a single layer.

Referring to FIGS. 1 and 2, the display device DD may include anon-light emitting area NPXA and light emitting areas PXA-B, PXA-G, andPXA-R. The light emitting areas PXA-B, PXA-G, and PXA-R each may be anarea emitting light generated from each of the light emitting elements(e.g., light emitting diodes) ED-1, ED-2, and ED-3. The light emittingareas PXA-B, PXA-G, and PXA-R may be spaced apart from one another on aplane (e.g., in a plan view).

Each of the light emitting areas PXA-B, PXA-G and PXA-R may be an areaseparated by the pixel defining film PDL. The non-light emitting areasNPXA may be areas between neighboring light emitting areas PXA-B, PXA-Gand PXA-R, and may correspond to the pixel defining film PDL. Meanwhile,in the present description, each of the light emitting areas PXA-B,PXA-G and PXA-R may correspond to a pixel. The pixel defining film PDLmay separate the light emitting elements (e.g., light emitting diodes)ED-1, ED-2 and ED-3. The emission layers EML-R, EML-G, and EML-B of thelight emitting elements (e.g., light emitting diodes) ED-1, ED-2 andED-3 may be disposed and separated in an opening OH defined in the pixeldefining film PDL.

The light emitting areas PXA-B, PXA-G, and PXA-R may be divided into aplurality of groups according to colors of light generated from thelight emitting elements (e.g., light emitting diodes) ED-1, ED-2, andED-3. In the display device DD of an embodiment illustrated in FIGS. 1and 2, three light emitting areas PXA-B, PXA-G, and PXA-R, which emitred light, green light, and blue light, respectively, are illustrated asan example. For example, the display device DD of an embodiment mayinclude a blue light emitting area PXA-B, a green light emitting areaPXA-G, and a red light emitting area PXA-R, which are distinct from oneanother.

In the display device DD according to an embodiment, the light emittingelements (e.g., light emitting diodes) ED-1, ED-2, and ED-3 may emitlight having different wavelength ranges. For example, in an embodiment,the display device DD may include a first light emitting element (e.g.,light emitting diode) ED-1 emitting blue light, a second light emittingelement (e.g., light emitting diode) ED-2 emitting green light, and athird light emitting element (e.g., light emitting diode) ED-3 emittingred light. That is, the blue light emitting area PXA-B, the green lightemitting area PXA-G, and the red light emitting area PXA-R of thedisplay device DD may correspond to the first light emitting element(e.g., light emitting diode) ED-1, the second light emitting element(e.g., light emitting diode) ED-2, and the third light emitting element(e.g., light emitting diode) ED-3, respectively.

However, the present disclosure is not limited thereto, and the first tothird light emitting elements (e.g., light emitting diodes) ED-1, ED-2and ED-3 may emit light in the same wavelength range or emit light in atleast one different wavelength range. For example, the first to thirdlight emitting elements (e.g., light emitting diodes) ED-1, ED-2, andED-3 may all emit blue light.

A first emission layer EML-B of the first light emitting element (e.g.,light emitting diode) ED-1 may include a first quantum dot complexQD-C1. The first quantum dot complex QD-C1 may be one that first quantumdots are combined with neighboring first quantum dots (e.g., neighboringfirst quantum dots are combined with one another). The first quantum dotcomplex QD-C1 may emit blue light, which is a first light.

A second light emitting layer EML-G of the second light emitting element(e.g., light emitting diode) ED-2 and a third light emitting layer EML-Rof the third light emitting element (e.g., light emitting diode) ED-3may include a second quantum dot complex QD-C2 and a third quantum dotcomplex QD-C3, respectively. The second quantum dot complex QD-C2 may beone that second quantum dots are combined with neighboring secondquantum dots (e.g., neighboring second quantum dots are combined withone another). The third quantum dot complex QD-C3 may be one that thirdquantum dots are combined with neighboring third quantum dots (e.g.,neighboring third quantum dots are combined with one another). Thesecond quantum dot complex QD-C2 and the third quantum dot complex QD-C3may emit green light, which is a second light, and red light, which is athird light, respectively.

In the present description, the quantum dot complexes QD-C1, QD-C2, andQD-C3 may each refer to a form in which a shell of a quantum dot iscombined with a shell of a neighboring quantum dot. The quantum dotcomplex QD-C will be described in more detail with reference to FIGS. 4Aand 4B.

In an embodiment, the first to third quantum dots of the first to thirdquantum dot complexes QD-C1, QD-C2, and QD-C3 included in the lightemitting elements (e.g., light emitting diodes) ED-1, ED-2, and ED-3respectively may be formed of different core materials. In anotherembodiment, the first to third quantum dots of the first to thirdquantum dot complexes QD-C1, QD-C2, and QD-C3 may be formed of the samecore material, or two quantum dots selected from the first to thirdquantum dots may be formed of the same core material, and the rest(e.g., a remainder thereof) may be formed of different core materials.

In an embodiment, the first to third quantum dots of the first to thirdquantum dot complexes QD-C1, QD-C2, and QD-C3 may have differentdiameters. For example, the first quantum dot utilized in the firstlight emitting element (e.g., light emitting diode) ED-1 emitting lightin relatively shorter wavelength ranges may have a relatively smalleraverage diameter than the second quantum dot of the second lightemitting element (e.g., light emitting diode) ED-2 and the third quantumdot of the third light emitting element (e.g., light emitting diode)ED-3, each emitting light in relatively longer wavelength ranges.However, the present disclosure is not limited thereto, and the first tothird quantum dots may be similar in size. In addition, the averagediameter of two quantum dots selected from the first to third quantumdots may be similar, and the rest (e.g., a remainder thereof) may bedifferent.

The light emitting areas PXA-B, PXA-G, and PXA-R in the display deviceDD according to an embodiment may be arranged in the form of a stripe.Referring to FIG. 1, a plurality of red light emitting areas PXA-R maybe arranged with each other along a second directional axis DR2, aplurality of green light emitting areas PXA-G R may be arranged witheach other along the second directional axis DR2, and a plurality ofblue light emitting areas PXA-B R may be arranged with each other alongthe second directional axis DR2. In addition, a red light emitting areaPXA-R, a green light emitting area PXA-G, and a blue light emitting areaPXA-B may be alternately arranged in turn along a first directional axisDR1.

FIGS. 1 and 2 illustrate that the light emitting areas PXA-B, PXA-G, andPXA-R are all similar in size, but the present disclosure is not limitedthereto, and the light emitting areas PXA-R, PXA-G and PXA-B may bedifferent in size from each other according to the wavelength range ofemitted light. Here, the areas of the light emitting areas PXA-B, PXA-G,and PXA-R may refer to an area when viewed on a plane defined by thefirst directional axis DR1 and the second directional axis DR2 (e.g., ina plan view).

Meanwhile, the arrangement of the light emitting areas PXA-B, PXA-G, andPXA-R is not limited to the one illustrated in FIG. 1, and the orderthat the red light emitting area PXA-R, the green light emitting areaPXA-G, and the blue light emitting area PXA-B may be arranged may havevarious suitable combination according to display qualitycharacteristics required for the display device DD. For example, thelight emitting areas PXA-B, PXA-G, and PXA-R may be arranged in the formof a Pentile™ or a diamond shape.

In addition, an area of each of the light emitting areas PXA-B, PXA-G,and PXA-R may be different in size from one another. For example, in anembodiment, the green light emitting area PXA-G may be smaller than theblue light emitting area PXA-B in size, but the present disclosure isnot limited thereto.

Referring to FIG. 2, the display device DD of an embodiment may furtherinclude a light control layer PP. The light control layer PP may blockexternal light incident to the display panel DP from the outside of thedisplay device DD. The light control layer PP may block some of theexternal light. The light control layer PP may perform a reflectionpreventing or reducing function to minimize or reduce reflection of(e.g., due to) external light.

In an embodiment, the light control layer PP may include a color filterlayer CFL. That is, the display device DD of an embodiment may furtherinclude the color filter layer CFL disposed on the light emittingelements (e.g., light emitting diodes) ED-1, ED-2, and ED-3 of thedisplay panel DP.

In the display device DD of an embodiment, the light control layer PPmay include a base layer BL and the color filter layer CFL.

The base layer BL may be a member providing a base surface on which thecolor filter layer CFL is disposed. The base layer BL may be a glasssubstrate, a metal substrate, a plastic substrate, etc. However, thepresent disclosure is not limited thereto, and the base layer BL may bean inorganic layer, an organic layer, or a composite material layer.

The color filter layer CFL may include a light blocking unit BM and acolor filter CF. The color filter CF may include a plurality of filtersCF-B, CF-G, and CF-R. That is, the color filter layer CFL may include afirst filter CF-B transmitting a first color light, a second filter CF-Gtransmitting a second color light, and a third filter CF-R transmittinga third color light. For example, the first filter CF-B may be a bluefilter, the second filter CF-G may be a green filter, and the thirdfilter CF-R may be a red filter.

Each of the filters CF-B, CF-G, and CF-R may include a polymerphotosensitive resin and a pigment and/or a dye. The first filter CF-Bmay include a blue pigment and/or a blue dye, the second filter CF-G mayinclude a green pigment and/or a green dye, and the third filter CF-Rmay include a red pigment and/or a red dye.

Meanwhile, the present disclosure is not limited thereto, and the firstfilter CF-B may not include a pigment or a dye. The first filter CF-Bmay include a polymer photosensitive resin, but may not include apigment or a dye. In some embodiments, the first filter CF-B may betransparent. The first filter CF-B may be formed of a transparentphotosensitive resin.

The light blocking unit BM may be a black matrix. The light blockingunit BM may be formed to include an organic light blocking materialand/or an inorganic light blocking material, both including a blackpigment and/or a black dye. The light blocking unit BM may prevent orreduce light leakage, and separate boundaries between the adjacentfilters CF-B, CF-G, and CF-R.

The color filter layer CFL may further include a buffer layer BFL. Forexample, the buffer layer BFL may be a protection layer protecting thefilters CF-B, CF-G, and CF-R. The buffer layer BFL may be an inorganicmaterial layer containing at least one inorganic material from amongsilicon nitride, silicon oxide, and silicon oxynitride. The buffer layerBFL may be formed of a single layer or a plurality of layers.

In an embodiment, the first color filter CF-B of the color filter layerCFL is illustrated to overlap the second filter CF-G and the thirdfilter CF-R, but the present disclosure is not limited thereto. In someembodiments, the first to third filters CF-B, CF-G and CF-R may beseparated by the light blocking unit BM and may not overlap one another.Meanwhile, in an embodiment, each of the first to third filters CF-B,CF-G and CF-R may be disposed correspondingly to each of the blue lightemitting area PXA-B, the green light emitting area PXA-G, and the redlight emitting area PXA-R.

In one or more embodiments, unlike the one illustrated in FIG. 2, thedisplay device DD of an embodiment may include a polarizing layer as alight control layer PP instead of the color filter layer CFL. Thepolarizing layer may block external light provided to the display panelDP from the outside. The polarizing layer may block some of the externallight.

In addition, the polarizing layer may reduce reflected light generatedin the display panel DP by external light. For example, the polarizinglayer may function to block reflected light in a case where lightprovided from the outside of the display device DD is incident to thedisplay panel DP and exits again. The polarizing layer may be acircularly polarizer having a reflection preventing or reducing functionor the polarizing layer may include a linear polarizer and a λ/4 phaseretarder. In one or more embodiments, the polarizing layer may bedisposed on the base layer BL to be exposed or the polarizing layer maybe disposed under the base layer BL.

FIG. 3 is a cross-sectional view schematically illustrating a lightemitting element (e.g., light emitting diode) ED according to anembodiment of the present disclosure.

Referring to FIG. 3, the light emitting element (e.g., light emittingdiode) ED according to an embodiment includes a first electrode EL1, asecond electrode EL2 facing the first electrode EL1, and a plurality offunctional layers disposed between the first electrode EL1 and thesecond electrode EL2 and including an emission layer EML.

The plurality of functional layers may include a hole transport regionHTR disposed between the first electrode EL1 and the emission layer EML,and an electron transport region ETR disposed between the emission layerEML and the second electrode EL2.

The hole transport region HTR and the electron transport region ETR eachmay include a plurality of sub functional layers. For example, the holetransport region HTR may include a hole injection layer HIL and a holetransport layer HTL as a sub functional layer, and the electrontransport region ETR may include an electron injection layer EIL and anelectron transport layer ETL as a sub functional layer. Meanwhile, thepresent disclosure is not limited thereto, and the hole transport regionHTR may further include an electron blocking layer as a sub functionallayer, and the electron transport region ETR may further include a holeblocking layer as a sub functional layer.

In the light emitting element (e.g., light emitting diode) ED accordingto an embodiment, the first electrode EL1 has electrical conductivity.The first electrode EL1 may be formed of a metal alloy or a conductivecompound. The first electrode EL1 may be an anode or a cathode. However,the present disclosure is not limited thereto.

In some embodiments, the first electrode EL1 may be a pixel electrode.The first electrode EL1 may be a transmissive electrode, a transflectiveelectrode, or a reflective electrode. When the first electrode EU is thetransmissive electrode, the first electrode EL1 may include atransparent metal oxide such as indium tin oxide (ITO), indium zincoxide (IZO), zinc oxide (ZnO), and/or indium tin zinc oxide (ITZO). Whenthe first electrode EL1 is the transflective electrode or the reflectiveelectrode, the first electrode EL1 may include Ag, Mg, Cu, Al, Pt, Pd,Au, Ni, Nd, Ir, Cr, Li, Ca, LiF/Ca, LiF/Al, Mo, Ti, a compound thereof,or a mixture thereof (e.g., a mixture of Ag and Mg).

In some embodiments, the first electrode EL1 may have a multilayerstructure including a reflective film or a transflective film formed ofthe above-described materials, and a transparent conductive film formedof indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO),indium tin zinc oxide (ITZO), etc. For example, the first electrode EL1may have a three-layer structure of ITO/Ag/ITO, but the presentdisclosure is not limited thereto. The first electrode EL1 may have athickness of about 700 Å to about 10000Å. For example, the firstelectrode EL1 may have a thickness of 1000 Å to about 3000 Å.

The hole transport region HTR is provided on the first electrode EL1.The hole transport region HTR may include a hole injection layer HIL, ahole transport layer HTL, etc. In addition, the hole transport regionHTR may further include at least one of a hole buffer layer or anelectron blocking layer in addition to the hole injection layer HIL andthe hole transport layer HTL. The hole buffer layer may compensate aresonance distance according to the wavelength of light emitted from theemission layer EML, and may thus increase luminous efficiency. Materialswhich may be included in the hole transport region HTR may be utilizedas materials included in the hole buffer layer. The electron blockinglayer is a layer that serves to prevent or substantially preventelectrons from being injected from the electron transport region ETR tothe hole transport region HTR.

The hole transport region HTR may have a single layer formed of a singlematerial, a single layer formed of a plurality of different materials,or a multilayer structure having a plurality of layers formed of aplurality of different materials. For example, the hole transport regionHTR may have a single-layer structure formed of a plurality of differentmaterials, or a structure in which a hole injection layer HIL/holetransport layer HTL, a hole injection layer H IL/hole transport layerHTL/hole buffer layer, a hole injection layer HIL/hole buffer layer, ahole transport layer HTL/hole buffer layer, or a hole injection layerHIL/hole transport layer HTL/electron blocking layer are stacked in therespective stated order from the first electrode EU, but the presentdisclosure is not limited thereto.

The hole transport region HTR may be formed utilizing various suitablemethods such as a vacuum deposition method, a spin coating method, acast method, a Langmuir-Blodgett (LB) method, an inkjet printing method,a laser printing method, and/or a laser induced thermal imaging (LITI)method.

The hole transport region HTR may include organic materials. Forexample, the hole transport region HTR may include, as an organicmaterial, any one from among carbazole-based derivatives such asN-phenyl carbazole and/or polyvinyl carbazole, fluorine-basedderivatives,N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine(TPD), triphenylamine-based derivatives such as4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA),N,N′-di(1-naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB),4,4′-cyclohexylidene bis[N,N-bis(4-methylphenyl]benzenamine (TAPC),4,4′-bis[N,N′-(3-tolypamino]-3,3′-dimethylbiphenyl (HMTPD),1,3-bis(N-carbazolyl)benzene (mCP), etc. However, the present disclosureis not limited thereto.

In addition, the hole transport region HTR may further include any onefrom among a phthalocyanine compound such as copper phthalocyanine,N,N′-diphenyl-N,N′-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4′-diamine(DNTPD), 4,4′,4″-(tris(3-methylphenylphenylamino)triphenylamine)(m-MTDATA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (TDATA),4,4′,4″-tris(N,-(2-naphthyl) -N-phenylamino)-triphenylamine (2-TNATA),poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS),polyaniline/dodecylbenzenesulfonic acid (PANI/DBSA), polyaniline/camphorsulfonic acid (PANI/CSA), polyaniline/poly(4-styrenesulfonate)(PANI/PSS), triphenylamine-containing polyetherketone (TPAPEK),4-isopropyl-4′-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate,dipyrazino[2,3-f: 2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile(HAT-CN), etc. However, the present disclosure is not limited thereto.

The hole transport region HTR may have a thickness of about 100 Å toabout 10000 Å, for example, about 100 Å to about 5000 Å. The holeinjection layer HIL, for example, may have a thickness of about 30 Å toabout 1000 Å, and the hole transport layer HTL may have a thickness ofabout 30 Å to about 1000 Å. For example, the electron blocking layer EBLmay have a thickness of about 10 | to about 1000 Å. When the thicknessesof the hole transport region HTR, the hole injection layer HIL, the holetransport layer HTL, and the electron blocking layer EBL satisfy theabove-described respective ranges, satisfactory hole transportproperties may be obtained without a substantial increase in drivingvoltage.

The emission layer EML is provided on the hole transport region HTR. Inthe light emitting element (e.g., light emitting diode) ED according toan embodiment, the emission layer EML may be formed from a quantum dotcomposition containing a plurality of quantum dots. The emission layerEML may include a quantum dot complex QD-C.

In the light emitting element (e.g., light emitting diode) ED accordingto an embodiment, the emission layer EML may include a host and adopant. In an embodiment, the emission layer EML may include the quantumdot complex QD-C as a dopant material. In addition, in an embodiment,the emission layer EML may further include a host material. In one ormore embodiments, in the light emitting element (e.g., light emittingdiode) ED according to an embodiment, the emission layer EML may emitfluorescence. For example, the quantum dot complex QD-C may be utilizedas a fluorescent dopant material.

The emission layer EML may have, for example, a thickness of about 5 nmto about 20 nm or about 10 nm to about 20 nm.

The emission layer EML may be formed utilizing various suitable methodssuch as a vacuum deposition method, a spin coating method, a castmethod, a Langmuir-Blodgett (LB) method, an inkjet printing method, alaser printing method, and/or a laser induced thermal imaging (LITI)method. For example, the emission layer EML may be formed by providingthe quantum dot composition of an embodiment through inkjet printing.

In the light emitting element (e.g., light emitting diode) ED of anembodiment, the electron transport region ETR is provided on theemission layer EML. The electron transport region ETR may include atleast one from among a hole blocking layer, an electron transport layerETL, and an electron injection layer EIL, but the present disclosure isnot limited thereto.

The electron transport region ETR may have a single layer formed of asingle material, a single layer formed of a plurality of differentmaterials, or a multilayer structure having a plurality of layers formedof a plurality of different materials.

For example, the electron transport region ETR may have a single layerstructure of an electron injection layer EIL or an electron transportlayer ETL, and may have a single layer structure formed of an electroninjection material and an electron transport material. In someembodiments, the electron transport region ETR may have a single layerstructure formed of a plurality of different materials, or may have astructure in which an electron transport layer ETL/electron injectionlayer EIL, or a hole blocking layer/electron transport layerETL/electron injection layer EIL are stacked in the respective statedorder from the emission layer EML, but the present disclosure is notlimited thereto. The electron transport region ETR may have a thicknessof, for example, about 200 Å to about 1500 Å.

The electron transport region ETR may be formed utilizing varioussuitable methods such as a vacuum deposition method, a spin coatingmethod, a cast method, a Langmuir-Blodgett (LB) method, an inkjetprinting method, a laser printing method, a laser induced thermalimaging (LITI) method, etc.

The electron transport region ETR may further include inorganicmaterials. In addition, the electron transport region ETR may include atleast one from among halogenated metals, lanthanide metals,co-deposition materials of a halogenated metal and a lanthanide metal.In some embodiments, the halogenated metal may be an alkali metalhalide. For example, the electron transport region ETR may include LiF,lithium quinolate (Liq), Li₂O, BaO, NaCl, CsF, Yb, RbCl, Rbl, Kl, and/orKl: Yb, but the present disclosure is limited thereto.

The electron transport region ETR may further include a mixture materialof an electron transport material and an insulating organo-metal salt.For example, the organo-metal salt may include, one or more metalacetates, metal benzoates, metal acetoacetates, metal acetylacetonates,and/or metal stearates.

The electron transport region ETR may include an anthracene-basedcompound. However, the present disclosure is not limited thereto, andthe electron transport region ETR may include, for example,tris(8-hydroxyquinolinato)aluminum (Alq₃),1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene,2,4,6-tris(3′-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine,2-(4-(N-phenylbenzoimidazolyl-1-ylphenyl)-9,10-dinaphthylanthracene,1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi),2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP),4,7-diphenyl-1,10-phenanthroline (Bphen),3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ),4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ),2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD),bis(2-methyl-8-quinolinolato-N1, O8)-(1,1-biphenyl-4-olato)aluminum(BAlq), berylliumbis(benzoquinolin-10-olate (Bebq₂),9,10-di(naphthalene-2-yl)anthracene (ADN), or a mixture thereof.

The electron transport layer ETL may have a thickness of about 100 Å toabout 1000 Å, for example, about 150 Å to about 500 Å. When thethickness of the electron transport layer ETL satisfies theabove-described ranges, satisfactory electron transport properties maybe obtained without a substantial increase in driving voltage.

When the electron transport region ETR includes the electron injectionlayer EIL, the electron injection layer EIL of the electron transportregion ETR may have a thickness of about 1 Å to about 100 Å, forexample, about 3 Å to about 90 Å. When the thickness of the electroninjection layers EIL satisfies the above-described ranges, satisfactoryelectron injection properties may be obtained without a substantialincrease in driving voltage.

The second electrode EL2 is provided on the electron transport regionETR.

The second electrode EL2 may be a common electrode. The second electrodeEL2 may be a cathode or an anode, but the present disclosure is notlimited thereto. In some embodiments, when the first electrode EL1 is ananode, the second electrode EL2 may be a cathode, and when the firstelectrode EU is a cathode, the second electrode EL2 may be an anode.

The second electrode EL2 may be a transmissive electrode, atransflective electrode, or a reflective electrode. When the secondelectrode EL2 is a transmissive electrode, the second electrode EL2 maybe formed of a transparent metal oxide, for example, indium tin oxide(ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide(ITZO), etc.

When the second electrode EL2 is a transflective electrode or areflective electrode, the second electrode EL2 may include Ag, Mg, Cu,Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF/Ca, LiF/AI, Mo, Ti, Yb, W, acompound thereof, or a mixture thereof (e.g., AgMg, AgYb, or MgAg). Insome embodiments, the second electrode EL2 may have a multilayerstructure including a reflective film or a transflective film formed ofthe above-described materials, and a transparent conductive film formedof indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO),indium tin zinc oxide (ITZO), etc. For example, the second electrode EL2may include the above-described metal material(s), a combination of twoor more metal materials selected from the above-described metalmaterials, and/or one or more oxides of the above-described metalmaterials.

In some embodiments, the second electrode EL2 may be connected with anauxiliary electrode. When the second electrode EL2 is connected with theauxiliary electrode, the electrical resistance of the second electrodeEL2 may decrease.

FIG. 4A is a cross-sectional view illustrating an emission layer EML1included in a light emitting element (e.g., light emitting diode) EDaccording to an embodiment in more detail. FIG. 4B is a cross-sectionalview illustrating an emission layer EML2 according to anotherembodiment.

The emission layers EML1 and EML2 may each include a plurality ofquantum dots QD1 and QD1-1. FIGS. 4A and 4B illustrate that the quantumdots QD1 and QD1-1 may be formed as two layers as an example, but thepresent disclosure is not limited thereto. For example, the arrangementof the quantum dots QD1 and QD1-1 may vary according to the thickness ofemission layers EML1 and EML2, the shape of the quantum dots QD1 andQD1-1 included in the emission layers EML1 and EML2, and the averagediameter of the quantum dots QD1 and QD1-1.

The plurality of quantum dots QD1 and QD1-1 included in the sameemission layer EML1 may include the same structure and the samematerial. However, for emitting light of a desired wavelength, thequantum dots QD1 and QD1-1 may include different structures and/ormaterials. Hereinafter, for the plurality of quantum dots QD1 and QD1-1,an arbitrary quantum dot QD1 will be described as an example.

The quantum dot QD1 may include a core CR1 and a shell SL1 around (e.g.,surrounding) the core CR1. However, the present disclosure is notlimited thereto. The shell SL1 may serve as a protection layer toprevent or reduce the chemical deformation of the core CR1 so as tomaintain (e.g., keep) semiconductor properties, and/or serve as acharging layer to impart electrophoresis properties to the quantum dotQD1. The shell SL1 may be a single layer or multiple layers. Aninterface between the core CR1 and the shell SL1 may have aconcentration gradient in which the concentration of an element presentin the shell SL1 becomes lower towards the center of the core.

The shell SL1 may include semiconductor compounds. For example, theshell SL1 may contain at least any one from among CdS, CdSe, CdTe, ZnS,ZnSe, ZnTe, ZnSeS, ZnTeS, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP,InGaP, InSb, AlAs, AIP, and AlSb. In some embodiments, the shell SL1 mayinclude at least one from among CdS, CdSe, CdTe, ZnS, ZnSe, and ZnTe.

In addition, the shell SL1 may further include a metal oxide and/or anon-metal oxide, for example, a binary compound such as SiO₂, Al₂O₃,TiO₂, ZnO, MnO, Mn₂O₃, Mn₃O₄, CuO, FeO, Fe₂O₃, Fe₃O₄, CoO, Co₃O₄, and/orNiO, and/or a ternary compound such as MgAl₂O₄, CoFe₂O₄, NiFe₂O₄, and/orCoMn₂O₄. However, the present disclosure is not limited thereto.

The core CR1 of the quantum dot QD1 may be selected from a Group II-VIcompound, a Group III-VI compound, a Group 1-III-VI compound, a GroupIII-V compound, a Group III-11-V compound, a Group IV-VI compound, aGroup IV element, a Group IV compound, and a combination thereof.

The Group II-VI compound may be selected from the group consisting of abinary compound selected from the group consisting of CdSe, CdTe, CdS,ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, and a mixture thereof,a ternary compound selected from the group consisting of CdSeS, CdSeTe,CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe,CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, anda mixture thereof, and a quaternary compound selected from the groupconsisting of HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe,CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, and a mixture thereof.

The Group III-VI compound may include a binary compound such as In₂S₃and/or In₂Se₃, a ternary compound such as InGaS₃ and/or InGaSe₃, or anycombination thereof.

The Group I-III-VI compound may include a ternary compound selected fromthe group consisting of AgInS, AgInS₂, CuInS, CuInS₂, AgGaS₂, CuGaS₂CuGaO₂, AgGaO₂, AgAlO₂, and any mixture thereof, and/or a quaternarycompound such as AgInGaS₂ and/or CuInGaS₂.

The Group III-V compound may be selected from the group consisting of abinary compound selected from the group consisting of GaN, GaP, GaAs,GaSb, AIN, AIP, AlAs, AlSb, InN, InP, InAs, InSb, and a mixture thereof,a ternary compound selected from the group consisting of GaNP, GaNAs,GaNSb, GaPAs, GaPSb, AINP, AINAs, AINSb, AIPAs, AIPSb, InGaP, InAIP,InNP, InNAs, InNSb, InPAs, InPSb, and a mixture thereof, and aquaternary compound selected from the group consisting of GaAINP,GaAINAs, GaAINSb, GaAIPAs, GaAIPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs,GaInPSb, InAINP, InAINAs, InAINSb, InAIPAs, InAIPSb, and a mixturethereof. In one or more embodiments, the Group III-V compound mayfurther include a

Group II metal. For example, InZnP, InGaZnP, InAlZnP, etc. may beselected as a Group III-II-V compound.

The Group IV-VI compound may be selected from the group consisting of abinary compound selected from the group consisting of SnS, SnSe, SnTe,PbS, PbSe, PbTe, and a mixture thereof, a ternary compound selected fromthe group consisting of

SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, and amixture thereof, and a quaternary compound selected from the groupconsisting of SnPbSSe, SnPbSeTe, SnPbSTe, and a mixture thereof. TheGroup IV element may be selected from the group consisting of Si, Ge,and a mixture thereof. The Group IV compound may be a binary compoundselected from the group consisting of SiC, SiGe, and a mixture thereof.

In this case, the binary compound, the ternary compound, and/or thequaternary compound may be present in particles in a uniformconcentration distribution, or may be present in the same particles in apartially different concentration distribution (e.g., nonuniformly).

The quantum dot QD1 may have a full width of half maximum (FWHM) of alight emission wavelength spectrum of about 45 nm or less, for example,about 40 nm or less, or about 30 nm or less, and color purity and/orcolor reproducibility may be enhanced when the full width of halfmaximum (FWHM) of the light emission wavelength spectrum is in the aboveranges. In addition, light emitted through the quantum dot QD1 may beemitted in all directions, and thus a wide viewing angle may beimproved.

In addition, the form of the quantum dot QD1 is not particularly limitedas long as it is a form commonly utilized in the art, and for example, aquantum dot in the form of spherical, pyramidal, multi-arm, or cubicnanoparticles, nanotubes, nanowires, nanofibers, nanoplatelets, etc. maybe utilized.

The quantum dot QD1 may control the color of emitted light according tothe particle size thereof, and thus the quantum dot QD1 may have varioussuitable light emitting colors such as blue, red, green, etc.

In the emission layer EML1 according to an embodiment, the plurality ofquantum dots QD1 and QD1-1 may be connected to each other to form aquantum dot complex QD-C. In some embodiments, when energy is providedto the emission layer EML1 to make the shell SL1 of the quantum dot QD1slightly melted (or softened), the slightly melted shell SL1 may becombined with at least one neighboring shell SL1-1 to form a quantum dotcomplex QD-C.

In an embodiment, referring to FIG. 4A, shells SL1 and SL1-1 of thequantum dots QD1 and QD1-1 included in the emission layer EML1 arecombined with shells SL1 and SL1-1 of all neighboring quantum dots QD1and QD1-1 to form one quantum dot complex QD-C layer. That is, in FIG.4A, the shells SL1 and SL1-1 of all the neighboring quantum dots arecombined together. In a case where the quantum dots QD1 and QD1-1 form asingle layer, when a composition for forming an electron transportregion ETR (FIG. 3) is applied onto the emission layer EML1 inmanufacturing a light emitting element (e.g., light emitting diode), thecomposition for forming the electron transport region ETR (FIG. 3) maybe prevented or substantially prevented from penetrating into theemission layer EML1, and accordingly, deterioration of devicecharacteristics due to current leakage may be prevented or reduced.However, the present disclosure is not limited thereto, and in anotherembodiment, as illustrated in FIG. 4B, the shell SL1 of the quantum dotsQD1 included in the emission layer EML2 is combined with the shell SL1-1of the neighboring quantum dot QD1-1. That is, in FIG. 4B, some portionsof the shells SL1 and SL1-1 of the quantum dots QD1 and QD1-1 are notcombined with the shells SL1 and SL1-1 of neighboring quantum dots.

When the quantum dots QD1 and QD1-1 included in the emission layer EML1form a bond between the shells SL1 and SL1-1, the combined shell of thequantum dot complex QD-C has a greater thickness than the shell SL1 ofthe single quantum dot QD1. For example, the shell SL1 of the quantumdot QD1 may have a thickness of about 1 nm to about 10 nm, and thecombined shell of the quantum dot complex QD-C may have a thickness ofabout 2 nm to about 20 nm. Here, the thickness of the shell SL1 of thequantum dot QD1 may refer to the shortest distance from a surface of thecore CR1 to a surface of the shell SL1. The thickness of the combinedshell of the quantum dot complex QD-C may refer to the shortest distancefrom a surface of the core CR1 of one quantum dot QD1 to a surface ofthe core CR1-1 of the (e.g., neighboring) quantum dot QD1-1 in thecombined structure.

In addition, when the quantum dots QD1 and QD1-1 included in theemission layer EML1 form a bond between the shells SL1 and SL1-1,dangling bond of the quantum dots QD1 decreases. Further, the distancebetween the neighboring quantum dots QD1 and QD1-1 becomes shorter, sothat the film density of the emission layer EML1 may be improved.

FIG. 5 is a flowchart illustrating forming an emission layer EML in amethod of manufacturing a light emitting element (e.g., light emittingdiode) ED according to an embodiment. FIG. 6 schematically illustratesproviding a preliminary emission layer P-EML (S200) in a method offorming an emission layer EML according to an embodiment. FIG. 7 is aview illustrating a portion of a quantum dot composition QCP provided inFIG. 6 in more detail. FIG. 8 is a view schematically illustratingproviding energy to the preliminary emission layer P-EML to form anemission layer EML (S300).

A method of manufacturing a light emitting element (e.g., light emittingdiode) according to an embodiment includes forming a first electrodeEL1, forming a hole transport region HTR on the first electrode EL1,forming an emission layer EML on the hole transport region HTR, formingan electron transport region ETR on the emission layer EML, and forminga second electrode EL2 on the electron transport region ETR.

In an embodiment, the forming of the emission layer EML includespreparing a quantum dot composition (S100), providing a preliminaryemission layer (S200), and providing heat to form an emission layer(S300).

The providing of the preliminary emission layer (S200) may refer toproviding a quantum dot composition QCP on the hole transport regionHTR. The quantum dot composition QCP may be provided between a pixeldefining layer PDL through a nozzle NZ. Meanwhile, in FIG. 6, the holetransport region HTR is illustrated to be provided as a common layer soas to overlap the pixel defining film PDL, but the present disclosure isnot limited thereto, and the hole transport region HTR may be providedbetween the pixel defining film PDL. For example, the hole transportregion HTR may be provided between the pixel defining film PDL,utilizing an inkjet printing method.

Referring to FIG. 7, the providing of the quantum dot composition QCPaccording to an embodiment may refer to dispersing quantum dots QD in anorganic solvent SV. In some embodiments, before the dispersing of thequantum dots QD in the organic solvent SV, binding (e.g., bonding)ligands LD to the quantum dots QD may be further included. When theligands LD are bonded to surfaces of the quantum dots QD, the quantumdots QD may have increased dispersibility in the organic solvent SV.However, the present disclosure is not limited thereto and the quantumdots QD may be dispersed in the organic solvent SV without the bindingof the ligands LD to the quantum dots QD.

In an embodiment, the organic solvent SV may include hexane, toluene,chloroform, dimethyl sulfoxide, cyclohexylbenzene, hexadecane, and/ordimethyl formamide. However, the present disclosure is not limitedthereto.

In an embodiment, the quantum dot composition QCP may further includelow melting point particles MP. The low melting point particles MP mayinclude a material having a low melting point, and for example, the lowmelting point particles MP may include a metal and/or an alloy having amelting point of 1300° C. or less. In some embodiments, the low meltingpoint particles MP may include a metal and/or an alloy having a meltingpoint of 800° C. or less. In the case where the low melting pointparticles MP are included in the quantum dot composition QCP, wheninducing the bonding between the shells SL of the quantum dots QD,reaction may be performed at a lower temperature. That is, the formingof the emission layer EML may be performed through a low temperatureprocess. In addition, materials constituting other layers, such as thebase substrate BS, the pixel defining layer PDL, etc. of the lightemitting element (e.g., light emitting diode) ED may be selected from abroader variety.

The low melting point particles MP are not particularly limited as longas the low melting point particles MP include a metal and/or an alloyhaving a melting point of 1300° C. or less, and in some embodiments, thelow melting point particles MP may include at least one from amongaluminum (Al), magnesium (Mg), zinc (Zn), tin (Sn), manganese (Mn),copper (Cu), and an alloy thereof.

The low melting point particles MP are not removed even after theemission layer EML is formed, and are included as doped (e.g., as adopant) in the emission layer EML, and thus may be included in an amountthat does not deteriorate the characteristics of the emission layer EML.For example, the low melting point particles MP and the quantum dots QDmay have a weight ratio of about 1:200 to about 1:20. Each of the lowmelting point particles MP may have a size of 1 μm or less. In someembodiments, each of the low melting point particles MP may have a sizeof 100 nm or less.

Referring to FIG. 8, after the preliminary emission layer P-EML isformed, energy is provided to the preliminary emission layer P-EML toform an emission layer EML. In this process, the shells SL of thequantum dots QD may be combined with each other to form a quantum dotcomplex QD-C. Accordingly, energy provided to the preliminary emissionlayer P-EML may be provided to form a bond (e.g., bonds) between theshells SL. The quantum dots QD have a nano size, and the quantum dots QDmay have lower melting points as compared to when materials included inthe shells SL have a bulk (e.g., larger) size. In addition, thepreliminary emission layer P-EML may further include more low meltingpoint particles MP to further lower the melting points. Accordingly,energy allowing the preliminary emission layer P-EML to have atemperature that reaches about 30% to about 80% of the melting point ofthe shells SL may be provided. In FIG. 8, the kind (e.g., type) ofenergy provided to the preliminary emission layer P-EML is illustratedas heat, but the present disclosure is not limited thereto, and forexample, light may be provided.

In one or more embodiments, when the ligands LD are bonded to thequantum dots QD and when energy is provided to the preliminary emissionlayer P-EML, the ligands LD may be dissociated and removed from thequantum dots QD. However, the present disclosure is not limited thereto,and some ligands LD may be present as being bonded to the quantum dotsQD.

In some embodiments, energy is provided to the preliminary emissionlayer P-EML to remove the organic solvent SV included in the quantum dotcomposition QCP. However, the present disclosure is not limited thereto,and evaporating the organic solvent SV may be further conductedthereafter.

FIGS. 9A and 9B are graphs showing results of analyzing luminousefficiency and lifespan of a light emitting element (e.g., lightemitting diode) according to the thickness of the shells. In FIGS. 9Aand 9B, G1 to G5 are quantum dots having the same material and sizeexcept for the thickness of the shells, and correspond to quantum dotshaving a shell that increases in thickness from G1 to G5.

Referring to FIG. 9A, it is confirmed that, with an increase inthickness of the shells, luminous efficiency increases. In addition,referring to FIG. 9B, it is confirmed that with an increase in thicknessof the shells, lifespan increases. Accordingly, it is expected that thelight emitting element (e.g., light emitting diode) according to anembodiment of the present disclosure may achieve suitable (e.g.,excellent) luminous efficiency and long life by forming a bond betweenneighboring shells to obtain greater thickness of the shells.

FIG. 10 is a cross-sectional view of a display device DD-1 according toanother embodiment of the present disclosure. Hereinafter, in thedescription of the display device DD-1 of an embodiment, duplicateddescriptions as one described above with reference to FIGS. 1 to 9B willnot be given again, and differences will be mainly described.

Referring to FIG. 10, the display device DD-1 according to an embodimentmay include a light conversion layer CCL disposed on the display panelDP-1. In addition, the display device DD-1 according to an embodimentmay further include a color filter layer CFL. The color filter layer CFLmay be disposed between the base layer BL and the light conversion layerCCL.

The display panel DP-1 may be a light emitting display panel. Forexample, the display panel DP-1 may be an organic electroluminescencedisplay panel or a quantum dot light emitting display panel.

The display panel DP-1 may include a base substrate BS, a circuit layerDP-CL provided on the base substrate BS, and a display element layerDP-EL1.

In an embodiment, the display element layer DP-EL1 may include a lightemitting element (e.g., light emitting diode) ED-a, and the lightemitting element (e.g., light emitting diode) ED-a may include a firstelectrode EL1 and a second electrode EL2 facing each other, and aplurality of layers OL disposed between the first electrode EL1 and thesecond electrode EL2. The plurality of layers OL may include the holetransport region HTR (FIG. 3), the emission layer EML (FIG. 3), and theelectron transport region ETR (FIG. 3). An encapsulation layer TFE maybe disposed on the light emitting element (e.g., light emitting diode)ED-a.

In the light emitting element (e.g., light emitting diode) ED-a, thesame description as the one described with reference to FIG. 3 may beapplied to the first electrode EL1, the hole transport region HTR, theelectron transport region ETR, and the second electrode EL2.

In the light emitting element (e.g., light emitting diode) ED-a includedin the display panel DP-1 of an embodiment, the emission layer mayinclude organic light emitting materials or may include the quantum dotcomplex described above. In the display panel DP-1 of an embodiment, thelight emitting element (e.g., light emitting diode) ED-a may emit afirst light. For example, the first light may be blue light.

The light conversion layer CCL may include a plurality of partitionwalls BK disposed spaced apart from each other and light control unitsCCP-G and CCP-R disposed between the partition walls BK. The partitionwalls BK may be formed from materials including a polymer resin and acoloring additive. The partition walls BK may be formed from materialsincluding a light absorbing material, and/or formed from materialsincluding a pigment and/or a dye. For example, the partition walls BKmay include a black pigment and/or a black dye to implement a blackpartition wall. When forming the black partition wall, carbon blackand/or the like may be utilized as a black pigment and/or a black dye,but the present disclosure is not limited thereto.

The light conversion layer CCL may include a light transmission unitCCP-B transmitting the first light, a first light control unit CCP-Gincluding a fourth quantum dot complex QD-C4 converting the first lightinto a second light, and a second light control unit CCP-R including afifth quantum dot complex QD-S5 converting the first light into a thirdlight. The second light may be light of longer wavelength ranges thanthe first light, and the third light may be light of longer wavelengthranges than each of the first light and the second light. For example,the second light may be green light, and the third light may be redlight. Regarding the quantum dots complexes QD-C4 and QD-C5 included inthe light control units CCP-G and CCP-R, the same descriptions as theone for the quantum dot complex described above may be applied.

The light conversion layer CCL may further include a capping layer CPL.The capping layer CPL may be disposed on the light control units CCP-Gand CCP-R, and the partition walls BK. The capping layer CPL may serveto prevent or reduce penetration of moisture and/or oxygen (hereinafter,referred to as “moisture/oxygen”). The capping layer CPL may be disposedon the light control units CCP-G and CCP-R to prevent or substantiallyprevent the light control units CCP-G and CCP-R from being exposed tomoisture/oxygen.

In an embodiment, the capping layer CPL may be an organic layer and/oran inorganic layer. For example, when the capping layer CPL includes aninorganic material, the inorganic material may include an alkali metalcompound such as LiF, an alkaline earth metal compound such as MgF₂,SiON, SiN_(x), SiOy, etc.

For example, when the capping layer CPL includes an organic material,the organic material may include a-NPD, NPB, TPD, m-MTDATA, Alq₃ CuPc,N4,N4,N4′,N4′-tetra(biphenyl-4-yl) biphenyl-4,4′-diamine (TPD15),4,4′,4″-tris(carbazol sol-9-yl)triphenylamine (TCTA), etc., and/or mayinclude epoxy resins and/or acrylates such as methacrylates.

The display device DD-1 of an embodiment may include a color filterlayer

CFL disposed on the light conversion layer CCL, and the descriptions ofFIG. 2 may be equally applied to the color filter layer CFL and the baselayer BL.

In the method of manufacturing a light emitting element (e.g., lightemitting diode) according to an embodiment of the present disclosure,when forming an emission layer, energy (e.g., specific energy) isprovided to induce bonding between shells of quantum dots, andaccordingly, the distance between the quantum dots in the emission layeris shortened to increase the stacking density of the quantum dots andthe thickness of the shells, thereby providing improved luminousefficiency and service life. In addition, the quantum dots may havereduced dangling bond, and the emission layer may thus have improvedthermal stability.

A light emitting element (e.g., light emitting diode) and a displaydevice according to an embodiment include quantum dots in which shellsof neighboring quantum dots are bonded to one another in the emissionlayers, and may thus exhibit improved luminous efficiency and servicelife.

A method of manufacturing a light emitting element (e.g., light emittingdiode) according to an embodiment may provide a light emitting element(e.g., light emitting diode) including an emission layer having suitable(e.g., excellent) stability, including bonding shells of neighboringquantum dots to each other. Although the present disclosure has beendescribed with reference to a preferred embodiment of the presentdisclosure, it will be understood that the present disclosure should notbe limited to these preferred embodiments but various changes andmodifications can be made by those skilled in the art without departingfrom the spirit and scope of the present disclosure, and equivalentsthereof.

What is claimed is:
 1. A light emitting diode comprising: a firstelectrode; a hole transport region on the first electrode; an emissionlayer on the hole transport region and comprising a quantum dot complex;an electron transport region on the emission layer; and a secondelectrode on the electron transport region, wherein the quantum dotcomplex comprises two or more quantum dots each comprising a core and ashell around the core, and of the two or more quantum dots, a shell ofone quantum dot is combined with a shell of at least one neighboringquantum dot.
 2. The light emitting diode of claim 1, wherein theemission layer further comprises low melting point particles, and thelow melting point particles comprise a metal and/or an alloy having amelting point of 1300° C. or less.
 3. The light emitting diode of claim2, wherein the low melting point particles comprise at least one fromamong Al, Mg, Zn, Sn, Mn, Cu, and an alloy thereof.
 4. The lightemitting diode of claim 2, wherein a weight ratio of the low meltingpoint particles to the two or more quantum dots is about 1:200 to about1:20.
 5. The light emitting diode of claim 2, wherein each of the lowmelting point particles has a size of 1 μm or less.
 6. The lightemitting diode of claim 1, wherein the shell comprises at least one fromamong CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnSeS, ZnTeS, GaAs, GaP, GaSb,HgS, HgSe, HgTe, InAs, InP, InGaP, InSb, AlAs, AlP, and AlSb.
 7. Thelight emitting diode of claim 1, wherein: the hole transport regioncomprises an organic material; and the electron transport regioncomprises an inorganic material.
 8. A display device comprising: aplurality of light emitting diodes; and a light conversion layer on theplurality of light emitting diodes and comprising at least one lightcontrol unit comprising a quantum dot complex, wherein the quantum dotcomplex comprises two or more quantum dots each comprising a core and ashell around the core, and of the two or more quantum dots, a shell ofone quantum dot is combined with a shell of at least one neighboringquantum dot.
 9. The display device of claim 8, wherein the lightemitting diodes are to emit a first color light, and the lightconversion layer comprises: a transmission unit to transmit the firstcolor light; a first light control unit to convert the first color lightinto a second color light; and a second light control unit to convertthe first color light into a third color light.
 10. The display deviceof claim 8, wherein the light control unit further comprises low meltingpoint particles, and the low melting point particles comprise a metaland/or an alloy having a melting point of 1300° C. or less.
 11. Thedisplay device of claim 10, wherein the low melting point particlescomprise at least one from among Al, Mg, Zn, Sn, Mn, Cu, and an alloythereof.
 12. The display device of claim 10, wherein each of the lowmelting point particles has a size of 1 pm or less.
 13. The displaydevice of claim 8, wherein the shell comprises at least one from amongCdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnSeS, ZnTeS, GaAs, GaP, GaSb, HgS,HgSe, HgTe, InAs, InP, InGaP, InSb, AlAs, AlP, and AlSb.
 14. The displaydevice of claim 9, further comprising a color filter layer on the lightemitting diodes, wherein the color filter layer comprises: a firstfilter to transmit the first color light; a second filter to transmitthe second color light; and a third filter to transmit the third colorlight.
 15. A method of manufacturing a light emitting diode, the methodcomprising: providing a first electrode; forming a hole transport regionon the first electrode; forming an emission layer on the hole transportregion; forming an electron transport region on the emission layer; andforming a second electrode on the electron transport region, wherein theforming of the emission layer comprises: preparing a quantum dotcomposition comprising a plurality of quantum dots having a core and ashell around the core; providing the quantum dot composition to form apreliminary emission layer; and providing energy to the preliminaryemission layer such that a temperature of the preliminary emission layerreaches about 30% to about 80% of a melting point of the shell.
 16. Themethod of claim 15, wherein the quantum dot composition furthercomprises low melting point particles.
 17. The method of claim 15,wherein the preparing of the quantum dot composition is performed bydispersing the plurality of quantum dots in an organic solvent.
 18. Themethod of claim 17, further comprising binding a ligand to the pluralityof quantum dot before the dispersing of the plurality of quantum dots inan organic solvent.
 19. The method of claim 18, wherein, in theproviding of energy to the preliminary emission layer, the ligand isdissociated from the plurality of quantum dots.
 20. The method of claim15, wherein the forming of the emission layer and the forming of theelectron transport region on the emission layer are performed throughinkjet printing.